1973 Imperial Le Baron

Let's hear all the gory details about your car and how it became alternative fuelled.
Imperial73
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1973 Imperial Le Baron

Post by Imperial73 » Fri Aug 11, 2006 6:50 pm

I am currently busy updating the underhood components of my car, a 1973 Imperial Le baron 4 door hardtop. It will be an LPG-only setup, almost all regular fuel components have been removed in the meantime. The engine is mostly stock, it is a rebuilt 1969 440 crank + block, with 73 heads. I have no recent pictures, but when I bought the car, it was a mess underhood, and the Impco 300 mixer right above of the exhaust manifold didnt help getting a smooth idle.

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The ignition system consists of a MSD Pro Billet dist, MSD 6AL module, MSD Blaster SS coil. The LPG is Impco model E with a 425 mixer and a Quadrajet throttlebody. I intend to use the (larger) thermoquad throttlebody in the future, but havent found the correct adapter plate yet.

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Frank
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Nice Chrysler!

Post by Frank » Mon Aug 14, 2006 2:09 pm

I'm a bit partial to Chrysler's big cars having already had a 1978 New Yorker. I believe you are looking for an Impco PN AA3 adapter (Adapter, AA3-37, Carter Thermo-Quad) and since it still appears in Impco's current catalog, it likely still available.

However, unless I'm mistaken, the Quadrajet bolt and bore pattern is the same as the Thermo-Quad pattern so your current carburetor should be fine as is. Are you having a problem hooking up cables and linkages to the Quadrajet throttle body? As both are spreadbore designs, both should flow similarly and I don't expect that you will have a performance improvement by switching to the Thermo-Quad throttle body. If you don't ever expect to use the Thermo-Quad again, you can probably sell the intact carburetor for a respectable price.

I would recommend that you switch the gas valve to PN AV1-1644-2 (lean gas valve) if you have not already done so. I believe your fuel economy will improve with this part. It is also an extremely easy upgradeto do.

Frank

Imperial73
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Post by Imperial73 » Mon Aug 14, 2006 6:26 pm

Frank,

The Q-jet indeed has the same bolt pattern, and hooking up the throttle linkage was very easy. Probably the kickdown will need adjusting later on. The reason I want the TQ back has mostly to do with aesthetics and personal taste, the TQ's base plate is wider.

The adapter plate is just hard to get over here, but it should be on its way according to my local supplier.

If I remember well, the 425 is already fitted with the leaner valve. With the previous 300-setup, the car already had both very good throttle response and very reasonable fuel economy for its size and weight.

Jacques

Frank
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Lean Gas Valve ID

Post by Frank » Mon Aug 14, 2006 8:05 pm

It's easy to check if you have the lean gas valve. If you remove the gas valve and turn it upside down, it should have a 4X4 on the tip:

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The standard gas valve has a "19" on the tip:

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When you say that the kickdown linkage may need adjusting later on, I hope you mean that it is hooked up but possibly out of adjustment. Torqueflite transmissions must have the kickdown linkage connected or damage to the transmission may result.

Imperial73
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Post by Imperial73 » Tue Aug 15, 2006 5:17 pm

Ok, thanks for the pics, I'll check on the mixer.

Frank wrote:I hope you mean that it is hooked up but possibly out of adjustment.
Yes, that's indeed what I meant. I'm not used to talking about cars in English, so sometimes my posts may seem confusing :oops:

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Post by Frank » Tue Aug 15, 2006 10:40 pm

Your English is fine. I just wanted to be sure that you didn't have any problems with your transmission. :wink:

Imperial73
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Post by Imperial73 » Sun Dec 03, 2006 7:18 pm

some of the stuff that went into the car:

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I relocated the ignition module and coil to the front end of the engine bay, and not shown on the picture is the MSD adjustable timing control.

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Some parts I needed proved to be a challenge to find. I will kick out the quadrajet becaus it's a leaky construction. A Thermoquad throttleplate will come instead of it.

I fired up the engine a few times but it will require some serious adjustment. Besides, it smoked tremendously on the right side, will need to look into that as well...

Also, I will rebuild a vaporizer that I recently bought from Franz.

Imperial73
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Post by Imperial73 » Sun Feb 04, 2007 2:44 pm

In the meantime, due to the weather, not much happened, but I found a few nice parts to further complete the engine bay.

To begin, a 71 dual snorkel air cleaner, which is lower than the 68 model I already had:

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I also found an unstamped Imperial pie tin, which would make a nice detail underhood:

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sample pic:

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And I just bought a very interesting mixer from Franz (was a pleasure to do business!):

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The special mixer shown at right was used on a laboratory project. I used it to test an 8.3 Liter Cummins Spark Ignited Diesel engine conversion to LPG. It has a SLIGHTLY modified #44 gas valve. This mixer and a stock model E vaporizer allowed this engine to pull 340 bhp at 2200 RPM with 1996 emission certifications. It has less than 20 hours running time, and was painted glossy black. It should work well for a slightly modified 5.7 GM or a stock 7.4 engine.

Furthermore, during the week, my fanshroud will be restored.

Imperial73
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Post by Imperial73 » Thu Apr 26, 2007 5:55 pm

I added an Edelbrock Performer intake manifold an an Optima Redtop battery. I gapped the spark plugs at approximately 0.055"

Today, I started the engine for the first time since all the mods were added. It started within 2 cranks, and the idle was really smooth, without much need of adjustment in mixture or timing. 16 degrees initial advance seemed to be perfect. Unfortunately, my exhaust analyzer wasn't working anymore, so no mixture check yet.

Hope I can drive the car soon (still a few checks to make on the tranny, brakes etc) so I can appreciate the performance of the new setup.

The information on this board proved to be very useful. So thanks to everybody here!

Imperial73
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Post by Imperial73 » Fri Apr 27, 2007 6:46 pm

Couldnt resist the temptation of a test drive today. The performance has obviously improved a lot, with very good throttle response. The MSD ignition works perfectly, even with the wide plug gap.

Imperial73
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Post by Imperial73 » Fri Jun 01, 2007 3:26 pm

After some fine-tuning, the mileage improved a lot, without any sacrifice in performance.


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Yesterday, I got a little brother for my 4 door. Unfortunately, it is a total bucket, but it will live on through its parts in 3 other Imperials in the Netherlands. And it was good for some funny pictures:

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Imperial73
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Post by Imperial73 » Mon Oct 01, 2007 1:32 pm

Besides some maintenance- and repair not really related to alternate fuels, I now have scored some interesting parts: a pair of 915 heads. These are 1967-only heads for 440 engines, with closed chamber design. This will significantly raise my current sorry CR of 8.2 to somewhere around 9. Also included in the purchase were a set of 1.81/2.14 ex/int Manley stainless steel valves. During next year, I will have these heads milled, fitted with hardened exhaust valve seats, and port-matched with my intake manifold.

Imperial73
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Post by Imperial73 » Wed Apr 16, 2008 2:51 pm


Frank
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Post by Frank » Wed Apr 16, 2008 4:31 pm

Your car certainly does sound good!

Is this you racing against a Dodge W200? postma friesland maybe?

http://www.youtube.com/watch?v=hgJMkl6Aa_0&NR=1

Imperial73
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Post by Imperial73 » Fri Apr 18, 2008 3:55 pm

Frank, actually, that's me racing against a friend in her W200. We help each other out a lot on our cars. I gave her a few seconds before hitting the pedal, but apparently not enough to be a gentleman :lol: :lol:

And thanks, the sound is actually quite addictive... next week, I'll have a new tranny (the current one is virtually gone) and a slightly higher stall converter. Cant wait to see how this will affect acceleration!

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